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HF-17280

PROJECT: HF-17280
DESCRIPTION: MAIN BOARD A0765111 COPIER A076 (E7 series)
BRAND: RICOH
STATUS: n
PROJECT START DATE: near 2015
LOCALISATION: DD
DOCUMENTATION: almost completely recreated
PCB: TPD57280
DIMENSIONS: 215 x 180 mm
CPU CATALOG NUMBER: UC-209
MEMORY CATALOG NUMBER: MM-125
VERSION: 1.00

HF-17280

Project Info

This is quite interesting 'retro' system with NEC UPD78312 with external memory, MMU, NVRAM, 2 PIO and a lot of drivers for servos...
RICOH made very well such classical electronics in early 1990s.
I reversed engineered this module, created block and circuit diagrams, downloaded and analyzed MM-125 ROM and even started to write my own software.
My development plans are to run THOS-1 operating system on this board.
Works goes very slowly. As usual I working at the same time for hundreds of similiar projects and HF-17280 have not priority.
More details about hardware can be found in DEVICE FILE [2] which is almost complete electrical circuit connection description.

MMU

On this board simple MMU is made with combinational circuit based on IC120 (7432), IC121 (74138) and IC123 (7411).
Processor is normally configured on internal memory (in UPD78312 you can see it examining PIN51 which is EA/ switch). CPU can also access external resources via multiplexed address/data bus.

Resources management:

ADDRESS	RESOURCE	SIZE	IC	REMARKS
0x0000-0xDFFF	EXTERNAL ROM READ	56K	IC116 (M27C512)	64KB, MM-125, RICOH A0775105A
0xE000-0xE3FF	EXTERNAL RAM WRITE	1K	IC130 (MK48Z12)
0xE400-0xE7FF	EXTERNAL RAM READ	1K	IC130 (MK48Z12)
0xE800-0xEBFF	RESET	1K	IC117	SOFTWARE -> HARDWARE RESET
0xEC00-0xEFFF	PIO1.CS/	1K	IC108 (UPD71055)
0xF000-0xF3FF	PIO2.CS/	1K	IC124 (UPD71055)
0xF400-0xF7FF		1K
0xF800-0xFBFF		1K
0xFC00-0xFFFF	TEST POINT CS/	1K

Instruction set

Both 78K and 87AD instruction sets are quite well designed and complex. Efficient code can be written. There is interesting one-byte instruction CALLT where function table can be created in zero page a can be called by one byte only. This is nice idea and can be used for writing efficient operating system.
BTW 78K and 87AD instruction sets are similiar but machine code is complietly other.

Version control

HF-17280 is still in its original version but mordenisation is planned. First of all I will switch CPU to external memory and similiar like in HF-17244 I will probably change DIP28 ROM to DIP32 flash memory (unfortunately DIP28 flash memories doesnt exist). HF-17280 doesnt support such change in anyway (no PCB options), so it is complicated but possible. Reason is obvious, erasing UV ROMs isn't convenient at all, while it is quite easy to program flash ROM. Some additional paths must be added what doesnt look nice but thats not a real technical problem.

VERSION	DESCRIPTION
1.00	original version
2.01	modernisation-1 (planned)

Sources:
[1] UPD78312 Datasheet
[2] HF17280 DEVICE FILE

STATUS CODES

f	failed
g	device not complete
n	not tested
p	planned
q	not accomplished
r	resigned
u	fully operational
w	assembled but not tested
x	not avalaible (returned, sold, lost or no data)
z	decomissioned (disassembled)

Prefix 17

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